TUBE AS 9V8978 - Caterpillar

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(1) Hystat motors (2) Return manifold (3) Engine (4) Front hystat pump (left side) (5) Rear hystat pump (right side) (6) Charge pump for the rear hystat pump (7) Implement pump (8) Front hystat charge pump and fan pump (9) Final drive
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(10) ECM (11) Backup alarm (12) Parking brake solenoid (13) Override solenoid (14) Solenoid for the rear hystat pump (forward) (15) Solenoid for the front hystat pump (forward) (16) Solenoid for the rear hystat pump (reverse) (17) Solenoid for the front hystat pump (reverse) (18) Left motor solenoid (19) Right motor solenoid (20) Brake pedal position sensor (21) "G-Port" pressure sensor (22) Engine speed sensor (23) Speed sensor for the right motor (24) Speed sensor for the left motor (25) Service brake pedal switch (26) Throttle position switch (27) Operator in seat switch (28) Parking brake switch (29) Hydrostatic joystick control (30) Thumb wheel (31) Speed recall button (32) Horn (33) Forward and reverse control (34) Steering controlThe hydrostatic drive system responds to inputs from the operator. Also, the hydrostatic drive system responds to inputs from the sensors. The hydrostatic drive system controls the following items:
The displacements of the hydrostatic drive pumps and motors
The output for the backup alarm
The state of the hydrostatic transmission override valve
The state of the parking brake valve
The engine start and the neutral interlock
The electronic fuel pump
The travel speed indicator
The ether starting aid
The air heater for the engine inletThe system also provides engine overspeed and underspeed protection. In an overspeed condition, the system automatically adjusts the current that is supplied to the hydrostatic pumps and motors in order to slow the machine. Engine underspeed protection is provided by decreasing the control currents to the hydrostatic pumps and to the motors. This is in response to the low engine speeds and to the engine lug.